Tag: weeds

I am now entering the 4th and final year of my PhD at Rothamsted Research and the University of Reading. My research, which is funded by the BBSRC and Lawes Agricultural Trust, aims to develop a model that will predict areas of a farmer’s field that are vulnerable to weed, in particular black-grass, invasion, and establishment. This work will contribute to the knowledge, and innovation, needed for more efficient use of herbicides.

Sometimes, as a scientist I am required to communicate my work to a larger audience. Often this can be tricky as it forces me to step outside of the world I frequent on a daily basis where everyone speaks the same language full of scientific jargon. I am forced to reconnect with the real world and translate my work into everyday English; something which is not always an easy task. Here is an overview of my project in what I hope is language that everyone can understand.

Farmers in the UK, and around the world, face many challenges. We often hear about problems of insect pests or deadly diseases destroying crops worldwide. But in fact, one of the biggest problems faced by farmers is weed control. When weeds grow in a field they not only take up valuable nutrients and water from the soil but can also compete with crops for light. This means the crop plants may not grow as large as they would do otherwise and so they produce less food.

Black-grass is a grass weed found in cereal crops, like wheat. It is extremely well-known to farmers across the country and in most of England, it is proving especially problematic.

As you walk around the southern and eastern English countryside in the summer you can see this weed growing across almost every wheat field you pass and farmers will be doing everything they can to get rid of it.

There are many ways that farmers are trying to reduce the amount of black-grass in their fields but currently chemical weed killer, or herbicide, is the most preferred. These chemicals can be applied to the bare soil in the autumn to try and prevent the weeds from emerging or they can be applied in the spring before the crop matures to kill off any weeds that have already started to grow.

In most cases a farmer will apply the chemicals uniformly across the whole field. This is nice and simple, you can drive your tractor up and down the field spraying as you go. However, when you are next out walking in the local countryside and you go through a wheat field I want you to take a look around for black-grass. It is usually nice and easy to spot with dark seed heads that stand just a bit taller than the crop.

Hopefully, you will notice something.

The weeds don’t grow uniformly across the field. Instead, they form patches of varying size and shape. This presents an opportunity for farmers to target where they apply their weed killer. Why should we be spraying the whole fields when the weeds are only growing in some parts of it?

These chemicals are expensive to buy and so any reduction in the amount of chemical applied to a field will have a direct financial benefit.

A reduction in the amount of herbicide used will also have environmental benefits by lessening the negative impacts on other organisms in the area – we don’t want to be damaging wild flowers in nearby hedgerows for example or polluting nearby water courses.

It seems simple doesn’t it? Only spray the chemicals where there is a problem with weeds. If you had a skin infection on your hand you wouldn’t expect to apply antibiotic cream over your whole body so why should we do the same thing to our farms?

Only it isn’t quite so simple. Do you remember I told you that the chemicals are often applied to the bare soil in autumn to try and prevent the weeds from coming up. So how would a farmer know which areas of the field to spray if he can’t see the weeds he is targeting?

One solution is to map the location of the weed patches in the field in summer and then apply the herbicide in the following autumn based on the map produced the previous year.

However, this option is not being readily taken up by farmers. Why could this be? It seems like a sensible option right?

Well, it could be that the farmers don’t want to risk missing weeds that grow outside of these mapped areas. The patches could expand or new seeds could enter the field carried by animals or farm machinery.

So how can we reduce this risk? How do we capture all the possible parts of the field that might have weeds growing whilst still reducing the total amount of chemical we apply to the land?

Well, like all organisms, the places in which black-grass grows are influenced by the environment. There are certain environmental conditions that are favourable to its growth and some which are not.

You wouldn’t expect to see a cactus growing in the Arctic would you?

This is an extreme example but the same principles apply.

We can identify certain environmental conditions, in particular to do with the soil that are favourable, or not, for black-grass.

The question I am trying to answer with my work is this: Can we find a way to predict which areas of a field are more or less favourable for black-grass? Does it prefer heavy, wet soils or sandy dry ones for example?

If we can identify areas of a field that are vulnerable, then we could choose to only spray weed killer on those areas. This would reduce the amount of herbicide use overall, and minimise the risk of missing weeds that grow outside of the patches mapped in the previous summer.

So, to recap, farmers face many challenges every day. In order to try and control weeds on their farms they will often apply chemical weed killer across the whole field. These chemicals come at great expense to the farmer and the environment. By targeting where these chemical are applied we can reduce this cost whilst still controlling the weed problem.

In order to understand what this means I find it is often easiest to break this down as it is only then that I can easily explain what I do.

Lets start at the beginning, shall we?

Modelling

No, I don’t strut around having my picture taken all day. I am talking about mathematical modelling. The sort where I take biological processes and describe them in a mathematical way and then using a programming language tell a computer how it can recreate those processes.

In order to do this I need data. Lots and lots of data. This means that whilst my main aim is the modelling I don’t just sit at my computer writing code. Instead I spend the bulk of my time out in the field or in a glasshouse conducting experiments to give me all of that data that I can feed into the model so that it provides realistic results and can simulate realistic scenarios.

the spatial variation

Many biological populations are not uniform and my study species is no exception. It forms patches of varying size and shape within fields and so I am studying the spatial variation in population density. I am also looking at how that variation relates to environmental properties which also vary in space.

in Alopecurus myosuroides

Alopecurus myosuroides is my particular study species. It’s common name in the UK is black-grass but it goes under many pseudonyms depending on where in the world you are. It is a particularly problematic weed of winter cereals in the UK and often has a patchy distribution within fields

for precision weed management

This is why I am doing the other stuff. It is the goal. If my project works and I find out some useful information it will be used for precision weed management. Simply put, this means changing your management practices according to where you are in the field.

So that is a breakdown of my title. I often find with research project titles, or journal article titles, that whilst they are rarely very catchy they do explain a great deal as to what will be covered in the following text. This is great when deciding whether you want to invest your valuable time in reading the thing but not so great if you want to draw people in who weren’t interested in the first place.

Recently I was asked to come up with a fun and catchy title to summarise my project to help advertise I talk I will be giving soon in a local pub. That’s when, after a lot of deliberating, I cam up with “Where the wild weeds are”. I feel like this is a much catchier title, and it is a lot more fun. Yet it still encompasses the essence of what I do. Why can’t all scientific titles be like this?

Next time: My talk in the local pub. How I convey my research to non-scientists